


Watching Kate

by missy520



Series: Watching [2]
Category: Castle
Genre: Double Penetration, Multi, Oral Sex, Threesome - F/M/M, Voyeurism
Language: English
Status: Completed
Published: 2016-02-17
Updated: 2016-02-19
Packaged: 2018-05-21 07:32:01
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 4,793
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6043354
Author URL: https://archiveofourown.org/users/missy520/pseuds/missy520
Summary: <blockquote class="userstuff">
              <p>From a prompt from Blackwing:<br/>AU. Castle and Beckett are together. When they find Hunt in his hotel room Castle can tell Beckett is turned on by the Brit and decides to give her what she wants and indulge in his own voyeuristic tendencies. It starts out with Beckett and Hunt fucking and Castle watching but if author prefers Castle eventually joins them.</p><p>Disclaimer: I don't own Castle</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> There are 3 chapters. I plan to post a chapter a day. 
> 
> Since this is an AU, I've changed the timeline of the episode a bit. The crime scene stuff happens in the morning, and they first meet Hunt during that first day. No Jacinda, since Castle doesn't feel the need to run off to Vegas.

Rick Castle had to laugh. Here he was, watching his girlfriend Kate Beckett fucking another man. It had been his idea, and fuck, he was enjoying it too. 

It had all started a few days ago. He and Kate had rolled up to the crime scene after a wild night of secret sex. Their sexual relationship was still kind of new, but they had quickly realized they liked to watch. So far, they had only indulged in watching porn together, and watching each other masturbate, but they had discussed the possibility of bringing a third person into bed with them. 

Then the case led them to a hotel room to track down a suspect, and he was just walking out of the shower. Castle tried to cover Kate’s eyes (and his own), but they both managed to get an eyeful. And it was an eyeful. The guy’s cock was huge! Rick knew he was well hung, but he thought this guy was even bigger. Fuck, Kate looked at it a lot more than was necessary. When he’d covered her eyes, Kate moved her head so she could see everything. And then they found out who he was. So not only was he good looking, and had an accent, but he was Scotland Yard. Shit. 

He was watching Hunt and Beckett flirt when he got a crazy idea. Maybe they should invite the Brit to be the other person in bed with them. Thinking about Kate getting fucked by that cock gave him an instant hard-on. They’d had a productive day, but they decided to leave when they realized that they would have a problem getting Nigel’s prints. He and Beckett went their separate ways, but he sneaked out of the loft after his mother and Alexis had gone off to bed. Kate let him in after his secret knock.

“You know, you can just knock, Double 07,” Kate smirked at him. She knew he loved the secret stuff – she remembered his stories of his love of James Bond. But that didn’t mean she couldn’t tease him. He walked into her apartment with a shit eating grin. 

“Yeah, but Kate, he’s the coolest! “ Now he smirked at her. She was barefoot, so she had to go up on tiptoes to kiss him. He grabbed her hips and lifted her up; her legs instantly went around his waist. Their kisses went from soft to hard in about five seconds as he carried her down the hall to her bedroom. As soon as he was close to the bed, he released her and she landed on her ass on the mattress. He quickly followed her down and they kissed some more. 

Since she was dressed in sweats and a tee shirt, he had her naked in seconds. He was sucking on her breasts as she reached for his belt. Soon, his pants were around his ankles as he moved down her body, sucking as he went. When he got to her pussy, he kissed it and then spread it open. He licked it from top to bottom very slowly. Kate’s hands were in his hair as he licked it over and over again. He started to pick up speed as her hands began to tug on his hair. He moved his tongue to her clit and started to suck on it. Her hands went slack, and her hips began to move. Recognizing her tells, he doubled the suction on her clit and she fell apart under him. He sat up so he could watch. 

She was beautiful, and all the more beautiful in her climax. He began to stroke his cock as she came back to earth. He still had his cock in his hands, and he was about to thrust it into her when he realized he needed a condom. He looked up and she had one in her hand. Laughing, he took it from her, ripped it open and had his cock sheathed quickly. He pushed her legs apart and then thrust it home. He almost came from the sensations but he managed to get himself under control. He pumped his cock in and out in a steady rhythm. Kate was moaning and put her fingers on her clit as he thrust. 

“Fuck, Kate, I’m coming!” he screamed out. He felt the come boiling in his balls as his climax built. 

“Babe, come with me!” she exclaimed. He could feel her walls grabbing his cock and that was it for him. He filled the condom as he watched her come too. He pulled out slowly and got out of bed to dispose of it. When he came back to bed, she was still touching herself as she came down from her high. He climbed in next to her, and pulled the bedding up. She got close to him, and put her head on his shoulder.

“Kate? Are you sleepy or can we talk?” he said. He felt her nod so he continued. “I had an idea today.”

“That can be dangerous, Castle!” she laughed. He fake pouted, and she rubbed his chest and said, “Continue.”

“Thank you. I noticed you staring at Hunt’s dick today, and it made me think – he might be a good candidate for the third party. You looked interested in him, and I think I’d like to watch you guys have sex. And he’d be leaving, and we wouldn’t have to worry about ever seeing him again. What do you think?”

“Castle, are you sure about this? I know we’ve had fun fantasying about doing this, but to really do it?”

“Yeah, Kate, I’m serious. And the more I think about it, the more Hunt makes sense. We won’t have to worry about awkward situations. And we don’t have to worry about him saying anything to a gossip columnist, or any reporter. I’m sure he’s interested in you, too. I really want to do this.”

“I’ve got to admit I do want to fuck him. But that’s it. And the thought of you being there while this happens may be weird to some people, but I love it. Okay, let’s do this!” She picked her head up and kissed him on the lips. She broke off the kiss and threw off the blankets and grabbed his cock. She stroked it with both hands and then she moved her body so she could suck his cock into her mouth. 

His hips bucked as she sucked on it. When she took it out, it was shiny with her saliva. She put one hand on his balls and the other on his cock and now he groaned. “Fuck, Beckett, you are so good at that.” She grinned at him and then sucked it down her throat. He tried to talk, but he found that he didn’t have a coherent thought. He couldn’t even move his arms to touch her at all. 

Beckett knew he was close; she could feel his cock getting ready to shoot his come down her throat. She was ready and then she felt his come erupt. She swallowed it all, relishing the salty taste of him. She let his softened cock slither out of her mouth and kissed her way up his body. When she reached his lips, she didn’t slow down – he loved to taste himself on her lips. Now she pulled the bedding up and settled down next to him. 

“So we agree – we’re going to invite Hunt to be our third party, right?” Kate asked quietly. Castle could do nothing more than nod. “Good,” she said as she drifted off to sleep. Castle’s very active imagination came up with all sorts of pictures of what that would be like. He fell asleep with a smile on his face.


	2. Chapter 2

**Summary for the Chapter:**

> Kate asks Hunt if he's interested in having sex with her while Castle watches. As if he'd really have to think about that.

**Notes for the Chapter:**

> Since Rick and Kate are a couple already, the scene with the black dress didn't happen. In fact, they solved the case really quickly so we can get with the action.

The next morning, they were at the precinct bright and early. Castle arrived about fifteen minutes after Kate, coffee in hand. He found Hunt standing next to the murder board with Kate and the guys, and they were all involved in solving the case. And before the day was done, they had managed to solve it. The guys took off early and Castle said good night to Kate and the Brit. 

After Castle left, Beckett and Hunt were discussing the case as he helped her dismantle the murder board. Just as Kate was going to ask if he wanted to go have a drink together, he turned to her and said, “Fancy getting a drink?” 

Kate grinned at him. “That would be great. When are you leaving?”

“Tomorrow. I’ve got to face the music in London, but I need some time to decompress.”

“Great. Let me go freshen up and then we can leave,” Kate answered. Once she was in the bathroom, she texted Castle with the details. After she was finished, she and Hunt grabbed a taxi and he agreed that a drink in his room was a great idea. 

They were at the hotel quickly, and went straight to his room. Once inside, she hid a grin, as she remembered Castle trying to prevent her from seeing anything. Hunt headed over to the mini bar and reached to get a bottle of scotch and looked at her with raised eyebrows. “I’ll have a tequila,” she informed him and he poured their drinks, walked over and handed her hers. They clinked glasses, and Kate said, “To friendship and getting justice.”

Hunt nodded and said, “To justice. Thank you, Kate. At least we got some for Natalie’s love. And I was able to get it for her. Now I sense you want to talk about something else,” he grinned. 

“I should have known you’d figure it out, Detective. Maybe we should sit down for this, okay?” The Brit nodded and sat down, motioning for Kate to sit next to him. But she stayed standing. “I’m not sure if you figured it out, but Castle and I are a couple. We’ve kept our relationship kind of quiet because our captain isn’t crazy about him, and she might use it to boot him from the precinct.”

“I thought the two of you had feelings for each other, but hadn’t done anything about it. But why tell me?”

“Because we want to ask you to do something. It might seem kind of weird, but would you mind having sex with me while Castle watches?” 

Hunt threw his head back and laughed. “Would I mind having sex with you? You’re kidding, right?”

“You did hear the part about Castle watching? Because otherwise, it’s not happening,” Kate said. 

He stopped laughing to say, “Yeah, I did hear that. Doesn’t bother me. I won’t lie, I’ve had a hard-on all day – you are gorgeous. And if he wants to watch, that’s okay. Maybe he’ll learn something,” he smirked. 

“Trust me, he doesn’t need the lessons. We just like to watch. We just couldn’t figure out how we could do this. Castle’s kind of famous, and the Nikki Heat books have made me sort of famous too. So we need you to never talk about this, okay?” She looked at Hunt, and he nodded. “Great. Let me text Rick.” She pulled her phone out of her pocket and sent the text off quickly. 

Hunt once again indicated the seat next to him, but Kate was too nervous to sit. She couldn’t believe this was actually going to happen! The knock on the door came quickly, and before Hunt could even get off the couch, Kate had the door open, and Castle strode in. All of a sudden, Kate had second thoughts. Were they really going to do this? And then, Castle closed the door behind him, took Kate’s face between his hands, and kissed her softly on the lips. He moved his lips to her ear, and whispered, “Kate, we don’t have to do this.” And that was the end of the nerves. 

She moved her head and kissed him back. Then she whispered to him, “No, I want to do this.” She took him by the hand, and escorted him to a chair near the bed. She started to unbutton his shirt, but he took her hands in his and stopped her. He turned her around, and Hunt was there. Kate didn’t need him to say anything; she started to unbutton Hunt’s shirt instead. When she was finished, she pushed it off and went to work on his belt and pants. Meanwhile, Hunt was doing his best to get her naked. He kept stopping to kiss her, but Kate was focused on getting as much of his clothing off his body first. She wanted to see if that quick glimpse of his cock was correct. She had stripped him of everything but his boxers when she turned to see Castle sitting on the chair near the bed. Beckett laughed when she saw him rubbing his bulge through his pants. 

“You should get naked too, Castle,” she laughed again as she turned back to Hunt. He finished with her buttons and zipper and then she was standing there in her black lace bra and thong. Hunt took her by her elbows and pulled her to him. He crushed his lips to hers in a bruising kiss. Kate moaned deep in her throat while she opened her mouth to him, allowing his tongue to enter. As she thrust her tongue into his mouth, she could taste the alcohol and moaned again. She put her hands on the waistband of his boxers and pushed them down his legs a bit; Hunt stopped kissing her long enough to push them the rest of the way down, and stepped out of them. And she discovered her quick view had been correct – his cock was huge!

Castle had quickly undressed himself and sat back down in the chair. Damn, Kate was beautiful. He knew many people wouldn’t understand how watching her fuck another man could turn him on. But he’d always been a bit of a voyeur. Watching others have sex was arousing and watching Kate Beckett with another man was making him hard. He put a hand on his cock and stroked up and down. He watched the other two kiss, and then Hunt moved to sit on the bed, with Kate standing between his legs. 

Hunt put his hands on her lace covered breasts, and then he reached behind her to undo her bra. Kate shrugged it off, and Hunt’s fingers went straight to her nipples, which he tugged and twisted until she threw her head back and groaned. He played with her nipples for a while, but soon he wanted more. He stood up, took her by the hand, and put her on the bed. He slowly removed her thong and then spread her legs as wide as they would go. “Fuck, Kate, you must really want this – you are fucking wet!” Almost as soon as he said that, he put his face next to her pussy and licked. He used one hand to hold her pussy lips open while his tongue feasted on her. He continued to lick her up and down, but he was avoiding one spot – her clit. 

Kate was getting frustrated. She knew he was doing this on purpose. “Fuck it, Hunt. If you don’t lick my clit soon, I will get my gun and shoot you between the fucking eyes!” He stopped what he was doing to look at her face, saw how serious she was and grinned at her.

“Alright, Kate, since you asked so nicely…” and then he pinched her clit. Her reaction was instantaneous; her back arched off the mattress and she wailed as she came. Hunt got off the bed while Kate came back to earth. When Hunt came back to the bed, he had a condom package in his hand. Kate took it from him, ripped it open, and covered his erection with it. Hunt climbed up on the bed and kissed Kate. She went to grab his cock but he stopped her. “Hold on a minute, Kate. Castle needs to see this.” So he sat on the bed near the headboard and stroked his cock a few times. “Turn around and face him so he can watch you ride my cock,” the Brit commanded. 

Castle loved this idea. He hadn’t wanted to say anything, but he had barely seen anything when Hunt was eating Beckett out. But now he could see Kate’s amazing body and he would be able to see Hunt’s cock a little more. Kate seemed to like this idea as well; she had a big smile on her face as she winked at Castle. He could see her toned legs tighten as she arranged herself over Colin’s erection. She put her hand on it as she guided it into her body. When she got all of it in, she moved her hips and then she slowly rode it up until it almost left her channel empty. 

Kate loved this position – she was in total control of how fast or how slowly she moved. And Hunt was using his hands in interesting ways; sometimes they were on her boobs, squeezing them or twisting her nipples, sometimes they were playing with her ass and sometimes they were creeping down to her pussy. And like Hunt had said, Castle could see her and she could see Castle, which was amazing. He was totally naked, and was stroking his cock very slowly. He gathered up the pre-come and spread it all over his shaft so his hands could move easier. She moaned loudly as she saw his cock get harder. 

Colin Hunt was just enjoying this weird sort of threesome. Kate was an amazing fuck; the least he could do is let Castle watch as his girlfriend rode another guy’s cock. While he couldn’t see much of Kate when she was in this position, he could see enough. Her ass was magnificent. He couldn’t resist putting his hands on it and he gave it a few smacks. He sat up a little more and moved his hands around her body so he could play with her breasts. All of a sudden, Kate froze, and he realized he could feel her walls clenching around his cock. “Oh fuck, Kate, I’m going to come!” he yelled as he felt his climax building. 

Beckett heard Hunt say something about coming, and that made her let go and come too. She could feel her mouth open but no sound came out. She felt his cock slide out of her body, and she went to her side as Hunt got up on his knees. She turned herself over and she watched him pull the condom off and then point his penis at her. Soon, she saw the come shoot out of his cock and land on her stomach and breasts. 

Castle had watched this with all of his attention. When Hunt pulled off the condom, and started to shoot come on Beckett’s body, he knew he had to get closer, and he had to add his load to her body. He got off the chair, cock in hand, and went to the side of the bed closest to Kate and stroked his cock until he came. His jism landed on her breasts. He and Hunt watched as Kate rubbed it into her body, mixing both loads together. She smiled at them while she gathered some of it in her hands and licked it off. 

“Fuck, Beckett. That was fucking hot!” Castle said. Hunt walked into the bathroom, and Castle climbed up on the bed. He couldn’t help it, he started to kiss Beckett. She put her hands on his semi-erect cock, and ran her hands around the base. He could feel it respond to her touch. And when one of her hands moved to his balls, he really responded. 

“So do I get to watch you two fuck?” Hunt said with a chuckle.


	3. Chapter 3

**Summary for the Chapter:**

> Now it's a threesome.

**Notes for the Chapter:**

> Last chapter.

Beckett turned her head to see Hunt standing next to the bed. “It’s up to you. But I was kind of hoping you’d join us,” she said. She went back to playing with Castle’s cock and balls. She could feel Castle’s cock responding to what she was doing, and she had a feeling he was also responding to the idea of Hunt joining them. She felt the mattress dip and turned her head and saw Hunt’s cock there. She didn’t think about it; she just sucked it into her mouth.

Castle couldn’t believe how much he was turned on right now. His girlfriend was sucking another guy’s cock right in front of him; right after the guy had fucked her to a mind blowing orgasm. And all he could feel was his cock getting harder by the minute. Kate’s hands were no longer playing with it, but he didn’t mind. He got off the bed to get a condom off the bedside table. He stood by the side of the bed watching Beckett blow Hunt while he put the condom on. Kate was now on her stomach as she sucked Hunt’s cock. Castle got back on the bed and grabbed Kate by the hips. 

Kate felt Rick’s hands on her hips and she understood what he wanted; she got up on all fours. Colin moved so she could continue to suck him off. She felt Rick run his cock through her folds right before he entered her with one strong thrust. 

He knew he wouldn’t last too long, so he didn’t waste any time on fancy moves. He just pumped his cock in and out of her body until he felt his climax building. “Fuck, Kate, I’m coming!” he screamed out. He felt her walls grab his penis until he felt his come fill the condom. 

She pulled Colin’s cock out of her mouth so she could scream as she orgasmed again. She felt Castle pull out and get off the bed. She thought he was going to the bathroom to dispose of the condom. Hunt’s cock was still close to her head, but she didn’t have the energy to move. He didn’t seem to mind; she saw him pull on it with his right hand. 

Hunt was glad he had asked Beckett for a drink; he was enjoying himself. And he wondered what would happen next. Kate was sprawled out on the bed, naked and glorious. He hoped he’d get to fuck her again. He watched as Castle walked back into the room after using the bathroom, his cock semi-erect. He grinned at the writer; Castle looked as curious as he felt. “So, Kate, any ideas for what we should do now?” he asked. She slowly put her head up, grinned, and nodded. 

“Grab condoms, guys. Rick, we need to get that cock nice and hard – I do see that you are halfway there. Colin looks ready for more,” she replied. She beckoned Castle to her, and he almost ran to the side of the bed. Kate just sucked it into her mouth. She knew through experience that it wouldn’t take her too long to get it hard, and she was right. She took it out before he could come. “Alright, Castle, get a condom on that dick, and then get on your back on the bed. I’m going to ride that cock while Colin fucks my ass!” She laughed at the look on Castle’s face – it was somewhere between shocked and aroused. Hunt just looked amused. 

No matter how much he was shocked, Castle was along for the fun. He got the condom on in record time, got on the bed, and waited for Kate to do what she wanted. He had his hand on the base of his cock while he watched her straddle his body. She took his cock in her hand, and guided it to her entrance. Soon he could feel his cock enter her. He let her control everything; he knew it would be great for him no matter what she did. 

Kate marveled at the sensations as she started to ride Rick’s cock. Sure, their sexual relationship was new, but she had never had a relationship like this before – every time was better than the time before. She loved how confident he was and how he often let her be in control of the action. The guys she had been with in the past had been bothered by her control freak tendencies; Rick just let her be herself. And right now, this self was feeling every ridge of that cock as it moved through her body. “Hunt, are you just going to stand there or are you going to do something?” she looked over her shoulder at the Brit. “Come on, do something!”

Hunt had to laugh. “Okay, Kate, I’ll do something!” He inserted one thick finger into her ass, and moved it in and out. Soon he added a second and a third. He had felt some resistance at first, but soon Kate was moaning and moving back to encourage him to move his fingers more. “Are you ready for more, Kate?” At her nod, he took his fingers out and put his cock at her entrance. He could hear the hiss as he slowly pushed his cock past her sphincter. “Sorry, Kate,” he apologized. 

“It’s okay, maybe if you go a little faster,” she said. He did, and the pain turned into pleasure. She looked down at Rick as soon as Colin was all the way in. Both men stopped moving to give Kate a chance to adjust, then they took turns moving. She felt so full; and it was amazing how one of them was inside while the other pulled out. Rick had moved a hand to her clit and was rubbing it with the right amount of pressure. 

Castle watched Beckett’s face – he knew she was close. So was he, but he wanted her to come before he did. So he pinched her clit between two fingers, and that was it. It was amazing to watch her climax and to feel it too. He let himself go and he followed her over the edge. He could feel the come erupting from his cock and then he heard Hunt.

“Fuck, Kate, your arse is so tight! And fuck, I’m coming!” He came with a shout, pulling out of Kate’s ass. He went back on his knees, and then onto his back on the bed. He watched as Kate collapsed on Castle’s chest, turning her head into his neck. 

Castle rubbed her back as her breathing got back to normal. She sat up, and got off Castle and climbed off the bed. Both men watched as she walked to the bathroom, unashamed of her nudity. Castle got off the bed, turned his back, and carefully disposed of the condom. He gathered up his clothing, and as soon as Kate returned, went into the bathroom.

Hunt watched Kate as she dressed, grinning at her the whole time. “Well, that was the most interesting drink I’ve ever had,” he said. Kate laughed as she moved over to the mirror to try to fix her hair. 

“Me too!” she replied. She watched as Colin got up and disposed of his condom, and walked over to her. He kissed her neck and she turned to give him a kiss on the cheek. “That was fun. But I’m sure you want to get a good night’s sleep before facing the music in London.”

“Yeah, I will. After all that exercise, I should sleep well!”

Castle walked back into the room just in time to see Kate throw her head back and laugh. She was dressed and looked like she was ready to leave. He felt a little awkward; what the fuck do you say to a guy who just helped you fuck your girlfriend? And is standing there naked? As usual, Kate took charge, and he just followed her lead. 

“Well, good luck with everything. If you’re ever in New York again, let us know. It might be fun to repeat this!” She grinned at both guys. Colin kissed her cheek, and then he and Rick just nodded at each other. Rick put his hand on the small of Kate’s back as they left the room.

As soon as they were in the elevator, Kate turned to him and kissed him on the lips. Before it could go too far, she pulled away. Rick grinned at her and said, “Now we need to find a woman to do that with!” Kate just rolled her eyes but she couldn’t help it, she grinned at him.

“Well, not tonight; I’m fucked out. But maybe tomorrow?” 

Castle just looked at her with a shocked expression. Best girlfriend ever!


End file.
